A large commercial aircraft may have a long wheelbase. The wheelbase is a distance along a centerline of the aircraft between nose gear and main gear of the aircraft. The long wheelbase of the aircraft may make it difficult to keep the main landing gear on a surface of a taxiway while executing a turn.
FIG. 1 is a prior art diagram depicting an aircraft 110 attempting to navigate a taxiway turn 100 with nose gear 112 of the aircraft 110 following a taxiway centerline 135. It may be desirable for gear 112, 114, and 116 of the aircraft 110 to remain on a surface of a taxiway 130 (i.e., between a left (outer) edge 132 of the taxiway 130 and a right (inner) edge 134 of the taxiway 130). However, when the nose gear 112 follows the taxiway centerline 135, the right main gear 116 may pass beyond the right (inner) edge 134 of the taxiway 130. The right main gear 116 may thus leave the surface of the taxiway 130. FIG. 1 shows that the taxiway 130 has been widened adjacent the right (inner) edge 134 of the taxiway 130 with an optional fillet 136. The optional fillet 136, if sufficiently wide, provides an additional paved surface to support the right main gear 116. Without the optional fillet 136, the right main gear 116 may leave the surface of the taxiway 130.
The nose gear 112 or the main gear 114 and 116 leaving the surface of the taxiway may create significant problems. For example, any of the gear 112, 114, and 116 leaving the surface of the taxiway 130 may jostle the aircraft 110 and cause injuries to passengers or damage to the aircraft 110 and its cargo. Further, if a shoulder of the taxiway 130 is soft, any of the gear 112, 114, and 116 rolling onto the shoulder may sink into the shoulder and the aircraft may become stuck. Because of these concerns, surfaces of some taxiways are widened at the turns (using fillets, such as the fillet 136) to try to maintain all the gear on the taxiway.
To keep the nose gear 112 and the main gear 114 and 116 on the taxiway 130, many operators “oversteer” the nose gear 112. Oversteering involves steering the nose gear 112 beyond a taxiway centerline 135 to try to ensure that the main gear on the inside of the turn (e.g., the right main gear 116 for a right-hand turn, as shown in FIG. 1) do not leave the surface of the taxiway 130. If the nose gear 112 is steered too far beyond the taxiway centerline 135, the nose gear 112 may roll off the surface of the taxiway 130. On the other hand, if the nose gear 112 is not steered far enough beyond the taxiway centerline 135, the right main gear 116 (for a right-hand turn, as shown in FIG. 1, or the left main gear 114 for a left-hand turn) may roll off the surface of the taxiway 130.